Variable valve actuation device for internal combustion engine

Abstract

In a variable valve actuation device for an internal combustion engine, a hollow boss ( 22 b ) is fitted around the outer periphery of an outer camshaft ( 15 a ) and protrudes from one side of a second cam ( 22 a ) located opposite a first cam ( 20 ) in the width direction of the second cam over a distance greater than the width of the second cam, in order to suppress misalignment of the boss.

The invention claimed is: 
     
       1. A variable valve actuation device far an internal combustion engine, far varying a phase difference between is pair of intake valves provided per cylinder of the engine or a phase difference between a pair of exhaust valves provided per cylinder of the engine, comprising:
 an assembled camshaft including a shaft member which is driven by an output from a crankshaft of the engine and which has a first cam formed thereon for actuating one of the pair of intake or exhaust valves, and a cam lobe having a second cam far actuating the other of the pair of intake or exhaust valves and fitted around the shaft member so as to be displaceable relative to the shaft member in a circumferential direction of the shaft member; and 
 a cam phase change unit configured to vary a phase of the second cam relative to that of the first cam, 
 wherein the cam lobe has a hollow boss fitted around the shaft member, 
 the boss protrudes from one side of the second cam located opposite the first cam in a width direction of the second cam over a distance greater than the width of the second cam, and has a connecting member connected to a control member for transmitting a variable cam phase, and 
 the connecting member is arranged in a position closer to an end portion of the boss opposite the second cam than to the second cam. 
 
     
     
       2. The variable valve actuation device according to  claim 1 , wherein one of the pair of intake valves or one of the pair of exhaust valves has, at an upper end thereof, a follower member that makes contact with the second cam, a width of the follower member in the axial direction of the second cam is larger than a width of the second cam, and
 wherein the connecting member is arranged in a position offset in the axial direction from the follower member. 
 
     
     
       3. The variable valve actuation device according to  claim 2 , wherein:
 the shaft member is constructed by rotatably fitting an inner camshaft as the control member through an outer camshaft, the assembled camshaft is configured such that the first cam is formed on an outer periphery of the outer camshaft, that the cam lobe having the second cam is rotatably fitted around the outer periphery of the outer camshaft, and that the connecting member connects the second cam and the inner camshaft to each other while allowing relative displacement of the outer and inner camshafts, the cam phase change unit is coupled to an end portion of the shaft member and causes the relative displacement of the outer and inner camshafts, 
 the cam lobe has a hold section that permits the assembled camshaft to be held in an orientation and 
 when the assembled camshaft is held in the orientation by using the hold section in order to couple the cam phase change unit to the end portion of the shaft member, the connecting member performs a function to prevent rotation of the inner camshaft. 
 
     
     
       4. The variable valve, actuation device according to  claim 3 , wherein the hold section is provided on the boss. 
     
     
       5. The variable valve actuation device according to  claim 4 , wherein the hold section is constituted by at least one pair of flat surfaces formed on an outer periphery of the boss and permitting the boss to be clamped. 
     
     
       6. The variable valve actuation device according to  claim 4 , wherein:
 the connecting member is a pin member inserted diametrically into the shaft member and penetrating through the boss and the outer and inner camshafts to connect the cam lobe and the inner camshaft to each other, 
 diametrically opposite portions of the outer periphery of the boss where a through hole for the pin member opens have flat seating surfaces respective surrounding open ends of the through hole through which the pin member is inserted, and 
 the hold section is constituted by the seating surfaces of the boss. 
 
     
     
       7. The variable valve actuation device according to  claim 1 , wherein:
 the shaft member is constructed by rotatably fitting an inner camshaft as the control member through an outer camshaft, the assembled camshaft is configured such that the first cam is formed on an outer periphery of the outer camshaft, that the cam lobe having the second cam is rotatably fitted around the outer periphery of the outer camshaft, and that the connecting member connects the second cam and the inner camshaft to each other while allowing relative displacement of the outer and inner camshafts, the cam phase change unit is coupled to an end portion of the shaft member and causes the relative displacement of the outer and inner camshafts, 
 the cam lobe has a hold section that permits the assembled camshaft to be held in an orientation, and 
 when the assembled camshaft is held in the orientation by using the hold section in order to couple the cam phase change unit to the end portion of the shaft member, the connecting member performs a function to prevent rotation of the inner camshaft. 
 
     
     
       8. The variable valve actuation device according to  claim 7 , wherein the hold section is provided on the boss. 
     
     
       9. The variable valve actuation device according to  claim 8 , wherein the hold section is constituted by at least one pair of flat surfaces formed on an outer periphery of the boss and permitting the boss to be clamped. 
     
     
       10. The variable valve actuation device according to  claim 8 , wherein:
 the connecting member is a pin member inserted diametrically into the shaft member and penetrating through the boss and the outer and inner camshafts to connect the cam lobe and the inner camshaft to each other, 
 diametrically opposite portions of the outer periphery of the boss where a through hole for the pin member opens have flat seating surfaces respectively surrounding open ends of the through hole through which the pin member is inserted, and 
 the hold section is constituted by the seating surface of the boss. 
 
     
     
       11. The variable valve actuation device according to  claim 1 , wherein:
 the shaft member is rotatably arranged above the cylinder, 
 the first and second cams are arranged adjacent to each other above the cylinder, and 
 at least part of a shaft section located between the adjacent first and second cams is used as a journal rotatably supported above the cylinder.